My definition of overrated is a little different than what most consider the term today, so I'll go on to explain that:

To me, overrated doesn't mean that the overrated person/group/thing isn't good, it just means they're given more credit than they deserve.

For example, Kobe Bryant is overrated. He's the best player in the NBA, but he's still overrated (being compared to the GOAT, Michael Jordan) Another would be Batman himself. He's the best comic book character, imo, but that doesn't mean that he isn't still overrated (Batman with prep =/= beat everyone)

What I take Nolan being overrated as is different, as well. He's made the best live-action Batman movie of all-time so far (TDK), but it isn't the definitive Batman on-film, from a comics-to-film perspective, as many would believe. There's so much missing from his series that others have, like the atmosphere of Gotham and the aesthetics of Batman's world that Bruce Timm and Tim Burton nailed, imo, and etc.